Photoflash lamp



July 20, 1965 J. w. SHAFFER 3,195,326

PHOTOFLASH LAMP Filed July 10, 1962 II II 1 JOHN W. SHAFFER INVENTORATTORN Y of their lamps.

United States Patent 3,195,326 PHOTOFLASH LAMP John W. Shatter,Wiiiiamsport, Pan, assignor to Syivania Electric Products line, acorporation of Delaware Filed Juiy It), 1962, Ser. No. 208,838

'4 Claims. (Cl. 67-31) This invention relates to the manufacture ofphotoflash lamps and more particularly to those photoflash lamps whichare provided with means for indicating the presence therein of moisturecontamination.

Generally speaking, a photoflash lamp comprises a hermetically sealedenvelope containing a source of actinic light, combustion-supporting gasand ignition means. The source of actinic light is usually in the formof shredded foil. The combustion supporting gas is usually oxygen. Theignition means usually comprises an incandescent filament supported by apair of lead-in wires and beads of fulminating material disposed on saidlead-in wires at the junctions of the filament therewith.

In the manufacture of photoflash lamps, the nature and quantity of theforegoing components thereof are regulated and controlled within veryclose tolerances to maintain a high degree of uniformity from lamp tolamp and thus insure the attainment of uniform light output and timingcharacteristics for each lamp type, all of which is well known andrecognized in the art. It has long been recognized and appreciated byflashlamp manufacturers that from time to time in the manufacture ofthese lamps, occasionally a lamp envelope is not completely hermeticallysealed and contaminating air enters the lamp. Sometimes these leakersare very slow in developing and are not detectable until long afterthese lamps have been shipped by the manufacturer.

In order to warn the ultimate user of flashlamps against using a leaker,some fiashlamp manufacturers have incorporated a readily visiblemoisture indicator in each These moisture indicators usually function ona change in color principle, i.e., when a lamp is truly hermeticallysealed, the moisture indicator will be of one color but, when exposed tomoisture-containing gas such as air, the color of the moisture indicatorwill change. The most commonly used moisture-sensitive material infiashlamp manufacture has been cobaltous cobaltic cyanide. When thismaterial is anhydrous, its color is dark blue. In the presence ofmoisture, it becomes lighter in color and finally changes to pink. Thusa flashlamp user is warned against using a fiashlamp, the moistureindicator of which is pink in color.

Over the years, the use of cobaltous cobaltic cyanide as themoisture-sensitive material of a moisture indicator has been reasonablysatisfactory. However, since cobaltous cobaltic cyanide is an insolublematerial, it requires a binding agent to hold it in place at the desiredlocus in the lamp and all of the binding agents used heretofore haveexhibited one or more undesirable characteristics which have adverselyaffected the efliciency of the mois- 7 forms of deterioration areevidenced by the flaking oif of the indicator from the surface to whichit has been applied. Other binding substances, which seem to adherewell, tend to be soft and susceptible to displacement to a varyingdegree by the abrasive action of the shredded foil during its insertioninto the lamp envelope. Still others are toxic and their commercial useshould be avoided.

Despite these recognized shortcomings, the use 'of 3,i5,32fi PatentedJuly 20, 1965 However, more recently the trend in the fiashlamp industryhas been to the use of smaller lamp envelopes having zirconium as theshredded foil combustible and gas fill pressures above atmospheric. Thiscombination of circumstances has resulted in an aggravation of some ofthe aforementioned deficiencies of the binding agents used heretofore toa point where they are no longer tolerable.

When zirconium is used instead of aluminum as the shredded combustiblefoil, a significant increase in its abrasive action on the moistureindicator binding agent as compared to aluminum is noted. This conditionis further aggravated, indirectly, by the increase in gas fill pressuresto superatmospheric because, since the gas and the combustible areusually maintained at or near stoichiometric balance, a substantialincrease in the density of the filling of combustible has occurred.

With smaller envelopes, such as less than 10 cc. volume for example, ithas been found that an inner protective lacquer coating is notnecessary, only an outside coating being needed. This elimination of theinside lacquer coating has posed a substantial problem insofar as themoisture indicator is concerned because now the moisture indicator mustbe one which adheres well to glass whereas heretofore it was applied tothe lacquer coating.

In view of the foregoing, one of the principal objects of this inventionis to provide a superiormoisture indi cator for photoflash lamps.

Another object of this invention is to provide a satisfactory moistureindicator for super-atmospheric photoflash lamps which employ zirconiumas the shredded combustible foil.

A further object of this invention is to provide a binding agent for aphotoflash lamp moisture indicator which does not substantially affectthe moisture-sensitive material thereof adversely.

These and other objects, advantages and features are attained, inaccordance with the principles of this invention, by using a colloidalmagnesium silicate as the binding agent for the moisture indicator infiashlamps. While I prefer to use colloidal magnesium silicate as thebinding agent, other colloidal magnesium silicates, such as for examplelithium-magnesium silicate and aluminum-magnesium silicate, may also beemployed satisfactorily.

The single figure of the drawing is an elevational view of one type ofphotoflash lamp provided with a moisture indicator in accordance withthe principles of this invention.

In the specific embodiment of the invention illustrated in theaccompanying drawing, the photoflash lamp illustrated therein comprisesa sealed, light-transmitting envelope 1 within which a quantity ofshredded zirconium foil 3 is disposed. The envelope 1 is provided with afilling of combustion-supporting gas, such as oxygen for example, at apressure of several atmospheres. Preferably, the combustible and thecombustion-supporting gas are substantially in stoichiometrio balance. Atungsten filament 5 is disposed within the envelope 1 and is attached tolead-in'wires '7 and 9 which are supported by and extend throughinsulator button 8. The inner ends of the lead-in wires 7 and 9 areprovided with a quantity of ignition paste 11. through an end of thelamp envelope and are bent into the form, of stirrups 13 and 15 lyingalong opposite sides of the press 17, the wires finally re-entering thepress 17 some distance away from the points at which they emerge.

The lead-in wires 7 and 9 extend The stirrups 13 and 15 defineelectrical contact members for engagement with electrical contactmembers of a fiashgun.

In the manufacture of a photofiash lamp of the type just described, thelamp envelope 1 is initially a segment of glass tubing, open at bothends. In the normal sequence of operations, the mount structure, whichcoma prises filament 5, lead-in wires 7 and 9 and insulator button 3, ispositioned in one of the open ends of the glass tubing and the'press 17is formed, thereby closing one of the open ends of the tubing. Asuitable applicator is then inserted into the remaining open end, of thetubing to provide the inner wall thereof with a moisture indicator spot19. Thereafter, a charge of combustible, in this instance shreddedzirconium foil, is introduced into the remaining open end of the tubing.,The envelope is then exhausted and provided with :a filling ofcombustionsupporting gas at several atmospheres pressure and finally theremaining open end is closed by drawing a tip 21. to

thereby define an hermetically sealed envelope.

The photofiash lamp illustrated in the accompanying drawing is of thetype identified commercially as an AG-l. The lamp envelope volume of anAG-l is about 1.5 cc.;

the gas pressure is about 4 /2 atmospheres; and the quantity of shreddedzirconium foil with which'the lamp is provided is about 20 mgs. per cc.of envelope volume.

On the other hand, one of the other more popular photo-1 flash lamps onthe market today is identified commercially as an M2. The lamp envelopevolume of an M2 is about 7.5 cc.; the gas pressure is about 1 /4atmospheres; and the quantity. of the combustible, in this case'shreddedaluminum foil, is about 2 mgs. per cc. of envelope volume.

From the foregoing, it is apparent that the. trend is to the use ofzirconium in place of aluminum as the combustible,

small envelopes, higher pressures and much greater den-1 sity'of thecombustible fill. Since zirconium shreds are much stiifejr, thanaluminum shreds of comparable dimen-- sions and since the fill densityof zirconium is much greater than thefill density of aluminum, theresulting significant increase in the abrasive action of the combos-- todegradation upon storage, either in the fiuid or dry form, by humidityor microbiological growth. The moisture-indicator spots formed with thismaterial as the binding agent not only adhere quite firmly to the glassenvelope but they are also hard enough to effectively resist theabraiding action .of zirconium foil much coarser than that presentlyused commercially as the combustible material. The thixotropic nature ofthe wet paste is also advantageous because it prevents running ordripping of the applied spot before drying.

By way of example, I have found that a highly satisfactory moistureindicator may be prepared'by combining a mixture of about 60% colloidalmagnesium silicate and about 40% cobaltous cobaltic cyanide by Weight inan appropriate vehicle, such as water or a water-alcohol solution.permntage of colloidal magnesium silicate used may be from about 95% toabout 10%, depending upon the desired degree of color inthe resultantindicating spot. The viscosity may be controlled to the desired tible onthe moisture indicator has rendered the binding agents used heretoforequite unsatisfactory for large scale commercial production.

During the search for a better binding agent for use in moistureindicator for photoflash-lamps, the following materials wereinvestigated: various natural and synthesis. glues; hydroxymethylcellulose; polyvinyl pyrollidone; polyvinyl alcohol, and other Watersoluble. or permeable polymers; soluble silicates such assodiumsilicate;

glass dust; colloidal alumina; emulsion-type binders including aurea-formaldehyde resin; and various salts such as the chlorides ofbarium, zinc, and strontium. Each of these materials exhibited one ormore of the previously described deficiencies.

I have found that colloidal magnesium silicates func-.

tion quite satisfactorily as a binding agent for moisture indicators, inphotofiash lamps without manifesting any of the undesirable propertieswhich characterize the previously mentioned materials and they adherequite well to the inner Wall of the glass envelope to which they areapplied. When colloidal magnesium silicate is used as they bindingagent, the moisture-indicating substance functions at nearly maximumsensitivity and much more elliciently than many of the materialspreviously used. Some of these binding agents decrease substantially thepotential sensitivity ofthe moisture-indicating material either by theformation of a relatively moisture-impermeable film around the particlesof the moisture-indicating'material or by the absorption of water by thebinding material itself. In either case, this increases the total amountof moisture needed to efiect a detectable color change in the indicator.

In addition, colloidal magnesium silicate is not adversely afiected byany temperatures that can be tolerated by the moisture-indicatingmaterial itself; nor is it subject level by adjusting the percentage ofsolids in the paste.

What I claim is:

1; A photoflashlamp comprising: a light-transmitting envelope; acombustion-supporting gas 'filling in said envelope; a quantity of afilamentary combustible disposed in saidenvelcpe; ignition meansdisposed in' said envelope in operative relationship with respect tosaid filamentary combustible; and a moisture indicator disposed in saidenvelope, said moisture indicator consisting essentially of a mixture'ofcobaltous cobaltic cyanide and a colloidal magnesium silicate.

2.?A photoflash lamp comprising: a light-transmitting envelope; acombustion-supporting gas filling in said envelope; a quantity offilamentary zirconium disposed in said envelopeyignition means disposedin said envelope in operative relationship with respect tosaidfilamentary zirconium; and a moisture indicator. disposed in saidenvelope, said moisture indicator consisting essentially ofamixtureotcobaltous cobaltic cyanide and a colloidal magnesium isilicate.

3. A photofiash lamp comprising: alight-transmitting envelope; acombustion-supporting gas filling in said envelope at a pressure aboveatmospheric; a quantity of filamentary zirconium disposed in. saidenvelope; ignition means disposed in said envelope in operativerelationship with respect to said filamentary zirconium; and a moistureindicator disposed in said envelope, said moisture indicator consistingessentially of a mixture, of cobaltous cobaltic cyanide and a colloidalmagnesium silicate.

4; A phototlash lamp comprising: a light-transmitting envelope; acombustion-supporting gas filling in said envelope at a pressure aboveatmospheric; a quantity of filamentary zirconium disposed in saidenvelope, said gas and said filamentary zirconium being substantially instoichiometric balance; ignition means disposed in said envelope inoperative relationship with respect to said filamentary zirconium; andamoisture indicator disposed in said envelope, said moisture indicatorconsisting essentially of a mixture of cobaltous cobaltic cyanide and acolloidal magnesium silicate.

References titted by theExaminer UNITED STATES PATENTS 1,131,432 3/15Smith 106-19 2,229,985 1/41 Nowak etal 117-222 2,281,758 5/42 Galat252-408 2,460,074 1/49 Davis 252-408 2,726,527 12/55 Pipkin 67-312,787,149 4/57 Gleim-et a1. 67-31 2,900,349 8/59 Swartz 252-3172,993,008 7/61 Anderson 67-31 FOREIGN PATENTS 584,463 10/59 Canada.

EDWARD J. l/IICHAEL, Primary Examiner.

FREDERICK L. MATTESON, IR Examiner.

1. A PHOTOFLASH LAMP COMPRISING: A LIGHT-TRANSMITTING ENVELOPE; ACOMBUSTION-SUPPORTING GAS FILLING IN SAID ENVELOPE; A QUANTITY OFFILAMENTARY COMBUSTIBLE DISPOSED IN SAID ENVELOPE; IGNITION MEANSDISPOSED IN SAID ENVELOPE IN OPERATIVE RELATIONSHIP WITH RESPECT TO SAIDFILAMENTARY COMBUSTIBLE; AND A MOISTURE INDICATOR DISPOSED IN SAIDENVELOPE, SAID MOISTURE INDICATOR CONSISTING ESSENTIALLY OF A MIXTURE OFCOBALTOUS COBALTIC CYANIDE AND A COLLOIDAL MAGNESIUM SILICATE.